Afterward he'll wonder why he didn't equip her with tentacles to begin with. >.>

Yay! :D Bitey sheep, with jaws full of teeth....

It's however you want it to manifest? It's constant outward cheerfulness/pleasantness. Inwardly, everyone can be as furious/upset/etc., as usual, but have no way of expressing it. So constantly smiling Nemu would totally be a possibility.

But for a week they can be a wonderful family unit!